Method of making an apertured dished article



Aug. 12, 1969 o. L. BROWN 3,460,368

METHOD OF MAKlNG AN APERTURED DISHED ARTICLE Filed March 27, 1967 2 Sheets-Sheet 1 0. L. BROWN METHOD OF MAKING AN APERTURED DISHED ARTICLE 2 Sheets-Sheet 2 Filed March 27. 1967 m/VJA/TOA Omar 1. 670a) Anne/v65! U.S. Cl. 72334 14 Claims ABSTRACT OF THE DISCLOSURE This disclosure describes a method of drawing sheet metal which is particularly adapted for forming an apertured dished section in a section of sheet material. The disclosed method includes the steps of forming a hollow dimple in the sheet material, deforming the dimple and the sheet metal immediately surrounding the dimple to at least partially collapse the dimple and form a dished section having a peripheral wall and a transverse end wall, and, if desired, removing the flattened dimple to form an aperture in the transverse end wall. The article so formed is integrally secured to the sheet metal therearound by a plurality of generally radially extending integral sheet metal webs. This disclosure also describes a method of forming a peripheral reinforcing rib on the dished article by bending the edges thereof and substantially simultaneously forming a groove in the surrounding area of sheet metal to prevent undue buckling and distortion of the surrounding section of sheet metal.

Background of the invention It is often necessary to form dished or cup shaped articles of sheet metal. The dished article or section has a peripheral wall and a transverse end wall or bottom wall integral with the peripheral wall. It is conventional practice to form such a dished section in a drawing operation utilizing a punch and a die.

One problem with the drawing operation is that the sheet metal often structurally fails adjacent the intersection of the peripheral wall and the transverse end wall. This is the result of thinning of the material and bending of the material at or adjacent this intersection.

In an attempt to overcome this problem, it is common practice to use progressive drawing steps to form the dished section. Progressive drawing however is relatively slow and increases the tooling cost as separate tooling is required for each stage of the operation.

Oftentimes, it is necessary or desirable to make a dished article of sheet metal with the dished article having an aperture through the transverse end wall thereof. This becomes necessary in making various articles such as washers, nut plates, etc. Such articles can be formed by a drawing operation following which an aperture is pierced in the transverse end wall thereof. As indicated above, the drawing operation tends to fracture the material at the intersection of the peripheral and transverse end walls.

However as the transverse end wall is ultimately pierced, it has been suggested to form an arcuate lance in the sheet metal prior to forming the dished section. The arcuate lance is sized to be of a size equal to the cut that is ultimately to be formed through the transverse end wall to form the aperture. The lance is located at the area in the sheet metal where it is desired to form the aperture. The lancing does tend to reduce the stress at the intersection of the peripheral wall and the transverse end wall and therefore tends to reduce the tendency of the dished section to fracture at this intersection. However, fracture does occur at the intersection and radially of the lance. Furthermore, when the dished section is formed, the loca- States Patent tion of the arcuate lance in the section of sheet material changes so that it no longer coincides with the desired location of the aperture. Thus, the lance shifts during the dish-forming operation so that the transverse end wall of the dished section is pierced at an area where it should not be. Furthermore, the shape of the lance may become somewhat distorted during the dish-forming operation. Similar fracturing and distortion occur when the aperture is pierced before the drawing or dish-forming operation is performed.

Still another background area is germane to the present invention. Articles of the kind described are frequently carried in a large section of sheet metal through various work stations. Sometimes prior to performing the last work operation on the article, several circumferentially extending slots are formed in the sheet metal around the article to thereby define a plurality of integral webs which secure the article to the surrounding region of sheet material. It is often necessary or desirable to reinforce the article by bending the edges thereof generally radially inwardly to form a peripheral reinforcing head. This bending pulls the webs and at least a portion of the surrounding region of sheet material inwardly. This inward pulling tends to distort the sheet metal radially outwardly of the slots. Such distortion prevents the section of sheet material from lying flat and hampers the work operations which are to be performed thereon at the various work stations.

Summary of the invention The present invention provides a method for making dished or cup shaped articles which eliminates structural failure of the sheet metal and the need for progressive drawing. The present invention also allows a deeper draw without the need for progressive drawing. In the case of an apertured dished article these results are obtained without the necessity for lancing or prepiercing of the sheet metal and no shifting or distortion of the aperture occurs. The present invention also substantially eliminates the problem of buckling and distortion of the sheet metal during the formation of a peripheral reinforcing rib on the article While the article is connected to the surrounding region of sheet metal by the radially extending webs. All of the above-noted advantages are accomplished without increasing the time or cost of manufacture.

One aspect of the present invention is to form a dished section or article in a section of sheet material without fracturing the sheet metal of the dished section. A basic concept of the invention is to offset a zone of sheet material to form a dished section having a transverse end wall and a peripheral wall while forcing at least some of the material of a central portion of the transverse end wall generally radially outwardly to provide additional material radially outwardly thereof to prevent fracture adjacent the intersection of the peripheral wall and the transverse end wall. It is also significant that such forcing of some of the material of the central portion radially outwardly exerts a radial outward force in the transverse end wall which further discourages separation or fracture adjacent the intersection of the peripheral wall and transverse end wall. The said central portion is thinned or otherwise distorted as a result of the forcing of at least some of the material thereof radially outwardly.

If the distortion of the central portion is undesirable, it may be flattened. In the event that it is desired to form an apertured dished article, the present invention teaches removal of this thinned or distorted central portion to form the desired aperture in the transverse end wall of the dished section.

According to the more specific teachings of the present invention, a portion of the sheet material is initially offset to form a hollow dimple in the sheet material, with the 3 dimple being surrounded by a circumscribing zone of the sheet material. Next, the circumscribing zone of the sheet material is deformed and the dimple is at least partially collapsed to form the dished section in the sheet material. During this deforming operation, the dimple is converted into at least a portion of the transverse end wall and the circumscribing zone is converted into the peripheral wall with the transverse end wall having an area in plan at least as large as the area in plan of the dimple. If the dished article is to be apertured, the collapsed dimple is then removed from the transverse end wall to form the aperture therein.

To conserve material in the region immediately surrounding the portion of the sheet material which is converted into the dimple, the present invention provides for substantially preventing drawing of material from the circumscribing zone into the dimple during the formation of the dimple. Thus, the sheet material is stretched and thinned during the dimple-forming operation, but substantially no stretching or thinning of the material of the circumscribing zone occurs. This thinning, however, has no effect on the structural strength of the resulting dished article at the intersection of the peripheral and transverse end walls because the thinned central portion lies radially inwardly of the intersection. Furthermore, in those instances where the article is to be apertured, the thinned portion of the sheet metal is removed to form the aperture in the transverse end wall. This drawing can be prevented, for example, by forming the dimple in a die that terminates outwardly in a frusto-conical section which is substantially flat radially. That is, the frusto-conical section will appear as a straight outwardly flared line in radial section.

During the formation of the dished section, the dimple is preferably completely collapsed. The collapsing of the dimple causes the material thereof to exert a radial outward force on the sheet material surrounding the dimple. This force assists in preventing fracture at the intersection of the peripheral wall and transverse end wall.

Additionally, the material of the flattened dimple has a thickness less than the original thickness of the sheet material, and to this extent the material of the dimple has been displaced radially outwardly into the region of material therearound. This additional material further tends to reduce the likelihood of fracture in the dished section. It should be noted that although the thickness of the flattened dimple is less than the original thickness of the sheet material from which the dimple is formed, the dimple itself may have portions which are thinner than the flattened dimple. This is because the overall wall area of the dimple is obviously significantly greater than the area of the flattened dimple, and accordingly, flattening of the dimple may actually cause the flattened dimple to have a greater minimum thickness than the minimum thickness of the dimple.

Another feature of this invention is to offset the dimple in one direction and to form the dished section in the other direction. Offsetting the dimple and dished section in this manner produces superior results. Furthermore, existing tooling will best permit the dimple and dished section to be formed in this manner.

A second aspect of the present invention is to prevent buckling or distortion of the sheet metal during the formation of a peripheral reinforcing rib on the dished article. This aspect of the invention is significantly related to the first described aspect of the invention in that it is frequently necessary or desirable to form such peripheral reinforcing ribs on apertured dished articles, such as washers.

According to the second aspect of the invention, a plurality of slots are formed in this sheet material to define a plurality of the members and a plurality of generally radial webs join each of the members to a surrounding region of the sheet material. An intermediate section of the sheet material is separated from adjacent articles by two of the slots. The peripheral zone of one of the articles is deformed to turn the edges of the article inwardly to form at least a portion of the peripheral reinforcing rib or section, with the inward turning of the edges forcing the webs and the surrounding region of sheet material inwardly.

To prevent such forcing of the webs and surrounding region of sheet material from buckling or distorting the section of sheet material, the present invention teaches the formation of a groove in the intermediate section. The axis of the groove is appropriately located so that the material surrounding the article can be pulled inwardly without interference from the intermediate section of sheet material.

Usually, these articles will be formed in an elongated strip of material having longitudinal edges and the intermediate section referred to above will extend laterally between the longitudinal edges of the strip. Similarly, the radially extending web may extend radially outwardly of the article and generally be perpendicular to the longitudinal edges of the strip.

The invention can best be understood by reference to the following description taken in connection with the accompanying illustrative drawings.

Brief description of the drawings FIG. 1 is a plan view of a reinforced washer or similar article constructed in accordance with the teachings of the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a fragmentary sectional view through a dimple die and punch and a section of sheet metal prior to formation of the dimple.

FIG. 4 is a fragmentary sectional view similar to FIG. 3 illustrating how the punch and die cooperate to form the dimple.

FIG. 5 is a fragmentary longitudinal sectional view through the punch and die utilized to convert the dimple and the sheet metal therearound into a dished section.

FIG. 6 is a fragmentary longitudinal sectional view through the tooling utilized to form the slots around the dished section and to form the aperture in the transverse end wall of the dished section.

FIG. 7 is a fragmentary plan view of the dished article following the work operation performed by the tooling shown in FIG. 6.

FIG. 8 is a top plan view similar to FIG. 7 after the reinforcing rib and the stress relieving groove have been formed.

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 8.

Description of the preferred embodiment Referring to the drawing, and in particular to FIGS. 1 and 2 thereof, reference numeral 11 designates a washer constructed in accordance with the teachings of this invention. The washer 11 is merely illustrative of the general type of articles to which the principles and teachings of the present invention are applicable.

The washer 11 is constructed of sheet metal, such as aluminum. The washer 11 has a circular end wall 13 with a central aperture 15 extending therethrough. A peripheral reinforcing rib 17 is formed as an integral part of the washer and surrounds the end wall 13. The reinforcing rib 17 is generally U- or V-shaped in cross section as shown in FIG. 2 and opens downwardly. As shown in FIG. 2, the end wall 13 is generally planar; however, the concepts of the present invention can be utilized Whether or not the end wall is planar.

FIGS. 3 and 4 illustrate the first step in producing a dished article, such as the washer 11. The first step of the method of this invention includes offsetting a portion 19 of a section 21 of sheet metal stock to form a hollow dimple 23, with the dimple being surrounded by a circumscribing zone 25 of the sheet material. The dimple 23 has a sloping dimple wall 27.

It is preferred not to draw material from the circumscribing zone 25 into the dimple wall 27 during the formation of the dimple. Thus, the dimple 23 is formed substantially by stretching of the portion 19 of sheet metal. Such stretching of the portion 19 will result in thinning of the sheet metal so that the dimple wall 27 will be thinner than the original thickness of the portion 19. For example, assuming the .018 inch thick aluminum sheet stock is used, the dimple wall 27 may have a thickness of about .011 inch at a crown 29 on the central axis thereof when the overall height of the dimple is .080 inch. This dimensional data, as is true of all dimensional data given herein, is presented solely by way of illustration and is not to be considered limiting in any way.

The dimple 23 is preferably formed by a dimple die 31 and a dimple punch 33. The die 31 has a cavity or recess 35 therein. The cavity 35 preferably has a generally cylindrical wall 37 that terminates outwardly in a frustoconical section 39. The frusto-conical section 39 is flared radially outwardly as shown in FIG. 3 and is described herein as being radially flat, which means that when viewed in section as shown in FIG. 3, the frusto-conical section 39 appears as a straight outwardly tapering line. This straight line forms an angle with a lower face 41 of the die 31 (FIG. 3) which may equal, for example, about 35 degrees. By providing the frusto-conical section 39, material from the circumscribing zone 25 is substantially prevented from being drawn into the dimple wall 27 during the formation of the dimple 23.

The punch 33 has a working face 43 which engages the lower face of the sections 21 of sheet metal and urges the portion 19 of sheet metal upwardly into the cavity 35 to form the dimple 23 as shown in FIG. 4. Of course, the die 31 and punch 33 are appropriately sized to produce a dimple of the desired height and diameter.

The next step of the present invention includes deforming the circumscribing zone 25 and at least partially collapsing the dimple 23 to form a dished section 45 (FIG. in the section 21 of sheet material. The dished section 45 has a peripheral wall 47 and a transverse end wall 49 which intersects the peripheral wall along a zone of intersection 51. As shown in FIG. 7, the dished article 45 and the transverse end wall are generally circular in plan, although it should be understood that various other shapes may be formed, if desired.

In the embodiment illustrated, the dimple 23 is completely collapsed and is converted into a flattened dimple or central portion 53 of the transverse end wall 49. The circumscribing zone 25 is converted into the peripheral wall 47 and into an annular zone 55 intermediate the peripheral wall 47 and the flattened dimple 53. The flattened dimple 53 has an area in plan which is substantially equal to and substantially coincident with the area in plan of the dimple 23. Thus, the dimple 23 does not shift relative to the other portions of the sheet material during the formation of the dished section 45. In the embodiment illustrated the transverse end wall 49 has an area in plan that is larger than the area in plan of the flattened dimple 53.

The importance of forming and collapsing the dimple is that during the collapsing thereof, the dimple exerts a radial outward force against the annular zone 55 which tends to resist separation or failure of the metal in the zone of intersection 51. Further, as explained more fully hereinbelow, some of the metal from the flattened dimple 53 flows radially outwardly into the annular zone 55 to further tend to prevent failure in the zone of intersection 51. It is apparent, therefore, that the height, diameter, and thickness of the dimple wall 27 can be varied as desired, depending upon the amount of outward push and/or metal flow into the annular zone 55 that is necessary or desirable to prevent structural failure of the material of the zone of intersection 51. In order that the full effect of collapsing of the dimple be utilized, it is preferred that the transverse end wall 49 completely contain the flattened dimple 53.

Although the section 53 of the transverse end wall 49 is referred to herein as a flattened dimple, it is apparent from viewing FIG. 5 that the section 53 is not completely flat, as the upper and lower surfaces thereof have several irregularities. As used herein, the expression flattened dimple is used to refer to a collapsed dimple, even though the surface contour thereof may appear somewhat irregular. I

The exact cross section of the flattened dimple 53 will vary somewhat from article to article and is diflicult to accurately show a typical cross section thereof. Accordingly, the flattened dimple 53 shown in FIGS. 5 and 6 is merely illustrative and some of the thinned areas thereof are exaggerated for clarity. Generally, however, assuming that the section of sheet metal 21 is approximately .018 inch, the flattened dimple 53 may have a thickness of approximately .015 inch along a line aa, approximately .0165 inch along a line b-b, and a thickness of approximately .013 inch along a central line cc, it being understood that the thicknesses along the lines aa and b-b extend completely around the flattened dimple 53. The metal thickness between the lines b-b and cc will vary, but should be less than .0165 inch and approach .013 inch. The thickness of the annular zone 55 immediately adjacent the flattened dimple 53 may be approximately .0165 inch and the thickness of the material at the zone of intersection 51 may be approximately .017 inch. These dimensions are given by Way of example to illustrate that the flattened dimple 53 has been thinned when compared with the original thickness of the portion 19 of sheet metal (FIG. 3) and when compared with the thickness of the annular zone 55, and accordingly, metal has flowed from the flattened dimple 53 radially outwardly into the annular zone 55. Thus, to the extent that the flattened dimple 53 is thinned, the annular zone 55' gains material and this material plays a significant role in preventing fracture of the material of the zone of intersection 51.

Another feature of this invention is the formation of the dimple 23 in one direction (upwardly as viewed in FIG. 4) and the formation of the dished section 45 in the other direction (downwardly, as shown in FIG. 5). It is believed that this feature of the invention further tends to reduce the tendency of the material of the zone of intersection 51 to fracture, and furthermore, tooling on existing equipment can more conveniently form the dimple and dished section in this manner.

The dished section 45 can be formed by any suitable tooling which substantially simultaneously collapses the dimple 23 to prevent fracture of the material of the zone of intersection 51. In the embodiment illustrated in FIG. 5, a punch 57 and a die 59 are utilized to perform this function. The die 59 has a cavity 61 of sufiicient area to receive the dished section 45 and may have a suitable vent opening (not shown). Similarly, the punch 57 has a working surface 63 sized and shaped to produce a dished section 45 of the desired configuration and dimensions.

The next step in the illustrated embodiment of the present invention includes removal of the flattened dimple 53 to form an aperture 65 in the transverse end wall 49 of the dished section 45 (FIG. 6). As the flattened dimple is removed to form the needed aperture 65 in the transverse end wall 49, the distortion and loss of material therein (FIG. 5) is of no consequence. In order to preserve the strength and continuity of the transverse end wall 49, it is preferred to completely remove the flattened dimple 53, and accordingly, the area in plan of the dimple 23, and hence the area in plan of the flattened dimple 53, should be appropriately sized to be no greater than the desired area in plan of the desired aperture 65. For some application where the effects of dimple flattenings are not objectionable, the dimple area in plan need not be sized with reference to the desired diameter of the aperture 65, as in these cases the aperture 65 may be formed by removing only a portion of the flattened dimple 53.

It is frequently desirable to mass produce the dished sections 45. To facilitate mass production, an elongated strip 67 (FIG. 7) of sheet material is sequentially advanced through several work stations which perform the several steps of the present invention. As it is much easier for the machines to work on the individual dished sections when the dished sections are integral with the strip 67, it is preferred to allow the dished sections to remain integral with the strip 67 until the last work operation 67 has been performed thereon, after which each of the dished articles may be severed from the strip 67.

With reference to FIGS. 6 and 7, a plurality of circumferentially extending slots 69 may be formed around the dished section 45 simultaneously with the removal of the flattened section 53. Alternatively, these slots 69 may be formed sequentially. If the slots 69 and the aperture are to be formed simultaneously, the tooling shown in FIG. 6 may be used. This tooling, which is merely illustrative, includes a die 71 having a central opening or recess 73 and a plurality of outer openings or recesses 75. The number of outer openings is selected to conform to the desired number of slots 69.

A cooperating punch 77 having a central cutting surface 79 and outer cutting surfaces 81 is provided to cooperate with the die 71. The openings 73 and 75 and the cutting surfaces 79 and 81 are sized and spaced to cooperate with each other in the manner shown in FIG. 6. Thus, by advancing the punch 77 toward the die 71, the cutting surfaces 79 and 81 engage selected areas of the sheet material to remove them from the strip 67. The openings 73 and 75 may be tapered as they extend downwardly to allow the flattened dimple 53 and the slugs 83 which have been removed from the strip 67 to fall into an appropriate receptacle (not shown).

FIG. 7 shows a typical arrangement of the slots 69. In FIG. 7, two relatively long diametrically opposed slots 69 and two relatively short diametrically opposed slots 69 define four generally radially extending webs 85 of sheet material which join the dished section 45 to a surrounding region 87 of sheet material. The dished section 45 is separated from an adjacent dished section 45' by an intermediate section or neck 89 which extends transversely between parallel longitudinal edges 91 of the strip 67.

As shown in FIGS. 6 and 7, the dished section 45 has an annular peripheral zone 93 surrounding the peripheral wall and integral therewith and with the webs 85. Also, as shown in FIG. 6, the transverse end wall 49 is generally parallel to the plane of the strip 67 and is offset therefrom by the peripheral wall 47.

The peripheral reinforcing rib 17 is formed by bending the peripheral zone 93 from the relatively fiat shape illustrated in FIGS. 6 and 7 to form the rib 17 shown in FIG. 9. As is apparent from viewing these figures of the drawings, the rib 17 is formed by turning of the peripheral zone downwardly and inwardly. The inner wall of the rib 17 is formed by the peripheral wall 47 of the dished sec tion 45. Thus, the peripheral zone 93 is bent substantially about its area of intersection with the peripheral wall 47. It is apparent that the rib 17 materially increases the strength and rigidity of the resulting article.

The inward bending of the peripheral zone 93 tends to pull the webs 85 and at least a portion of the surrounding region 87 radially inwardly. If this effect of forming the rib 17 were to be ignored, the strip 67 would be substantially distorted and it would be difficult to perform the various work operations thereon. According to the teachings of the present invention, a stress relieving groove 95 is formed in the intermediate section "89 with the axis of the groove extending in the longitudinal direction. The groove may be formed by forcing the metal of a portion of the intermediate section either upwardly or downwardly, as desired; however, downwardly is preferred. The importance of the groove is that it facilitates or accommodates the inward movement of the portions of the surrounding region 87 which are pulled inwardly. This prevents any substantial distortion of the strip 67.

The strip 67 is advanced through a work station which simultaneously forms the groove 95 and the rib 17 on successive dished articles. Thus, the dished article immediately upstream of this work station has no groove 95 or rib 17. The inward pull exerted on the surrounding region 85 during the rib forming operation tends to pull the edges 91 inwardly toward each other and the formation of the groove allows slight inward movement of the edges 91. Thus, the strip 67 is slightly wider upstream of this work station; however, this reduction in width of the strip 67 is not suflicient to introduce any significant distortion to the strip.

The groove 95 may be formed in whatever portion of the surrounding region 87 in which it can best accommodate the inward movement of the metal of the surrounding region. Similarly, the groove 95 must be appropriately oriented to accommodate such inward movement of portions of the surrounding region 87. In the embodiment shown, the webs 85 extend radially outwardly and are generally transverse to the longitudinal edges 91 of the strip 67. Thus, as the webs 85 are pulled inwardly, they exert an inward force on the surrounding region 85 which tends to draw the longitudinal edges 91 inwardly. To accommodate this movement, the groove 95 should preferably be oriented substantially as shown. It will be apparent that if the webs 85 were substantially parallel to the longitudinal edges 91, the orientation and, perhaps, location of the groove 95 would have to be altered.

No tooling is illustrated for forming of the groove 95 and for the inward bending of the peripheral zone 93, as these operations can be performed by conventional tooling.

In the final step of the method of the present invention, the washer 11 or other dished article formed, is severed completely from the strip 67.

Although an exemplary embodiment of the invention has been shown and described, many changes, modifica tions and substitutions can be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

I claim:

1. In a method of forming a dished section in sheet material, the steps of:

offsetting a portion of the sheet material in one direction to form a hollow dimple in the sheet material with the dimple being surrounded by a circumscribing zone of the sheet material; and

deforming said circumscribing zone of the sheet material in a direction generally opposite to said one direction and at least partially collapsing said dimple to form a dished section in the sheet material having a transverse end wall offset from the plane of the sheet material and a peripheral wall by converting the dimple into at least a portion of the transverse end wall and by converting at least a portion of said circumscribing zone into the peripheral wall with the transverse end wall having an area in plan at least as large as the area in plan of said dimple.

2. In a method of forming a dished section in sheet material, the steps of:

deforming a portion of the sheet material to form a hollow dimple in the sheet material with the dimple being surrounded by a circumscribing zone of the sheet material; and

offsetting said circumscribing zone of the sheet material from an adjacent surrounding region of sheet material while at least substantially flattening at least a major portion of said dimple to form a dished section in the sheet material having a generally flat transverse end wall offset from said surrounding region of the sheet material and a peripheral Wall with at least the flattened portion of the dimple forming at least a portion of the transverse end wall and with at least a portion of said circumscribing zone forming the peripheral wall.

3. A method as defined in claim 2 wherein said step of flattening includes at least substantially completely collasping said dimple.

4. A method as defined in claim 3 wherein the transverse end wall has a larger area in plan than the area in plan of said dimple and the flattened dimple is located generally centrally of said transverse end wall.

5. In a method of forming a dished section of sheet material, the steps of:

deforming a portion of the sheet material to form a hollow dimple in the sheet material with the dimple being surrounded by a circuscribing zone of the sheet material; and

offsetting said circumscribing zone of the sheet material from an adjacent surrounding region of sheet material and at least substantially collapsing said dimple to form a dished section in the sheet material having a transverse end wall offset from the surrounding region of the sheet material and a peripheral wall by converting the dimple into at least a portion of the transverse end wall and by converting at least a portion of said circumscribing zone into the peripheral wall with the transverse end Wall having an area in plan at least as large as the area in plan of said dimple.

6. A method as defined in claim 5 including substantially preventing drawing of material from said circumscribing zone into said dimple during said step deforming.

7. A method as defined in claim 1 wherein said dimple is completely flattened during said step of deforming and the transverse end wall is generally flat, and including the steps of removing the flattened dimple from the transverse end wall, substantially preventing drawing of material from said circumscribing zone into said dimple during said step of offsetting and turning the edges of said dished section inwardly to form a peripheral reinforced section on said dished section.

8. A method as defined in claim 5 including the step of removing said portion of the transverse end wall to form an aperture in the transverse end wall.

9. In a method of forming an apertured dished section in sheet material, the steps of:

offsetting a portion of the sheet material to form a hollow dimple in the sheet material with the dimple having a dimple wall and being surrounded by a circumscribing zone of the sheet material;

at least substantially flattening said dimple to cause some of the material in said dimple wall to flow generally radially outwardly into said circumscribing zone to provide additional material in said circumscribing zone;

offsetting said circumscribing zone to form a dished section having a peripheral wall and a transverse end wall with said transverse end wall having the flattened dimple therein; and

removing the flattened dimple from the transverse end wall to form an aperture therein.

10. In a method of forming an apertured dished section in sheet material, the steps of providing a die having a recess therein and terminating outwardly in a frusto-conical section which is substantially flat radially;

forcing a portion of the sheet material into said receSS of said die to form a hollow dimple in the sheet material, with the dimple being surrounded by a circumscribing zone of the sheet material and with the frusto-conical section substantially preventing drawing of material from said circumscribing zone into said dimple; and

deforming said dimple and said circumscribing Zone of the sheet material to generally collapse the dimple and to form a protrusion in the sheet material having a transverse end wall containing said flattened dimple and a peripheral wall.

11. In a method of forming a plurality of peripherally reinforced apertured members from sheet material wherein one of the members has a generally flat peripheral zone surrounding the aperture and is attached to the surrounding region of the sheet material by a plurality of webs extending between said peripheral zone and this surrounding region and said one member is spaced from the adjacent member by an intermediate section of the sheet material, the steps of:

bending said peripheral zone to move the periphery thereof inwardly to form at least a portion of a peripheral reinforcing rib on said one member with the inward movement of said periphery tending to pull said webs and at least a portion of the surrounding region inwardly and substantially simultaneously forming a groove in said intermediate section to facilitate the inward movement of the portion of the surrounding region.

12. In a method of forming a plurality of peripherally reinforced members from sheet material, the steps of:

forming a plurality of slots in the sheet material to define one of the members and a plurality of generally radial webs joining said one member to a surrounding region of the sheet material with an intermediate section of the sheet material separating one of the slots from an adjacent member;

deforming a peripheral Zone of said one member to turn the edges thereof inwardly to form at least a portion of a peripheral reinforcing section for said one member with the inward turning of the edges forcing the webs and the surrounding region of the sheet material inwardly; and

forming a groove in said intermediate section to prevent said material of said intermediate section from substantially resisting the inward movement of the webs and the surrounding region.

13. A method as defined in claim 12 wherein said members are formed in an elongated strip of sheet stock having longitudinal edges with the intermediate section extending between said longitudinal edges and the webs extending generally radially toward said longitudinal edges, and the groove is formed with an axis extending generally longitudinally.

14-. A method as defined in claim 12 wherein said one member is a dished section and is formed by offsetting a portion of the sheet material to form a hollow dimple in the sheet material with the dimple being surrounded by a circumscribing zone of the sheet material, deforming said dimple and said circumscribing zone of the sheet material to form the dished section in the sheet material with the dished section having a transverse end wall by converting the dimple into at least a portion of the transverse end wall, and removing said portion of said transverse end Wall to form an aperture therein.

References Cited UNITED STATES PATENTS 1,368,565 2/1921 Limont 72340 2,989,936 6/1961 Farnsworth et al. 72-335 3,123,910 3/1964 Neilson 72--356 RICHARD J. HERBST, Primary Examiner US. Cl. X.R. 72-335, 348 

